1. Field of the Invention
This invention relates to a seal structure of a compressor for use in an air conditioner and so forth.
2. Description of the Related Art
In compressors in general, constituent members that constitute a main housing are joined to one another and are fixed under this state by a plurality of bolts. An O-ring or a gasket seal is interposed into each joint portion in order to prevent pressure reduction.
Japanese Unexamined Patent Publication (Kokai) No. 8-261150 or 9-42156 discloses a seal structure for forming a multiple structure of O-rings or gasket seals. In the latter reference, two O-rings as seal members are interposed into the joint portions between members constituting a main housing. Because two O-rings are interposed, the sealing performance inside the housing can be improved.
However, the seal structure of the prior art is not free from the problem that when a high pressure gas such as carbon dioxide is used as a refrigerant, the carbon dioxide gas is likely to leak from the joint portion through a rubber material even when the O-ring made of the rubber material is constituted into the multiple structure, because carbon dioxide gas can easily permeate through the rubber material.
This problem may be solved by using a rubber material that has heat-resistance, oil resistance, blister resistance and gas permeation resistance in good balance, for the O-ring. However, it is practically difficult to select a material having all these functions, and even if the O-ring has a single-layered structure, the material cost becomes high.
In a multiple stage structure using the conventional rubber material, O-rings having the same diameter are stacked in multiple stages. When the diameter of the O-rings is increased in order to secure sufficient seal performance, the thickness of the housing must be increased at the seal portion, increasing the size of the housing. Even if the diameter of the O-ring is increased, the problem of the gas leak remains unsolved when the refrigerant is carbon dioxide.